FIG. 1 shows a drawing illustrating the essential part of the configuration which has been used so far. Such a configuration is shown, for example, in "Fine-grained Polysilicon and its Application to Planar Pressure Transducers," by H. Guckel, et al., TRANSDUCERS '89 PROCEEDINGS Vol. 2, pp.346 to 351.
In FIG. 1,
Number 11 shows a silicon substrate, 12 a measuring diaphragm made of polysilicon forming air gap chamber 13 together with the silicon substrate. Number 14 shows a piezo-resistance strain gage formed on the surface of measuring diaphragm 12. Number 15 shows a connecting hole provided in measuring diaphragm 12 and connects air gap chamber 13 to the outside. Number 16 shows a polysilicon thin film which fills connecting hole 15.
In this configuration, air gap chamber 13 is constructed by forming a solid part corresponding to air gap chamber 13 with silicon oxide film, then removing silicon oxide film using selective etching from connecting hole 15 which connects air gap chamber 13 to the outside, and filling connecting hole 15 with polysilicon thin film 16 formed by reduced-pressure chemical vapor deposition (CVD). The adoption of a reduced-pressure CVD retains air gap chamber 13 as a virtually sufficient vacuum for the reference pressure for the absolute pressure sensor.
However, in such equipment,
(1) Since internal stress is likely to exist because measuring diaphragm 12 is composed of polysilicon, the stiffness of the measuring diaphragm changes due to heat treatment. PA0 (2) Since piezo-resistance strain gage 14 must be formed on polysilicon measuring diaphragm 12, its sensitivity becomes low. PA0 (1) A semiconductor pressure sensor comprising a single crystal silicon substrate; a closed air gap chamber having a predetermined narrow gap which backs up an overpressure application to a diaphragm provided with the single crystal silicon substrate and forming a measuring diaphragm made by epitaxial growth; and a strain detection element incorporated in the above-described measuring diaphragm composed of a single crystal. PA0 (2) A manufacturing method for a semiconductor pressure sensor in which an air gap chamber is incorporated within a single crystal silicon substrate, wherein the following processes are included:
The present invention intends to solve these problems.
Although it is not easy to form single crystals of silicon on silicon oxide film, in recent years, a good silicon-on-insulation (SOI) wafer has become available because of the development of semiconductor processing techniques.
The present invention has been contrived by paying attention to such a situation. The purpose of this invention is to provide a highly reliable semiconductor pressure sensor having good accuracy and sensitivity and its manufacturing method, whose measuring diaphragm is composed of epitaxially grown single silicon crystals.